Conventionally, in spinning processes, yarn which is fed from a spinning machine and is being wound onto a winder, for example, or traveling yarn in other spinning and weaving processes or in the laboratory are measured, and defects relating to evenness or uniformity of the yarn, for example thick irregularities or thin irregularities, are detected, and furthermore periodic irregularities and the amount of hairiness are detected.
For example, there is known a device for detecting the thickness of yarn by passing traveling yarn between a pair of electrodes which are arranged facing each other, and by measuring the electrical capacitance detected by the electrodes (referred to as an electrical capacitance measuring device hereinbelow). On the other hand, as shown in U.S. Pat. No. 3264922, there is known a device for measuring the thickness of yarn by passing traveling yarn between a light source comprising a lamp and a light receiving means comprising a photocell, which are arranged facing each other, and by measuring the amount of light detected by the light receiving means (referred to as an optoelectric measuring device hereinbelow).
However, such conventional electrical capacitance measuring devices and optoelectric measuring devices only measure the overall yarn, including the core part of the yarn (main part of the yarn), and the thin hairs which project from the surface of said core part, and they are therefore unsuitable for measuring yarn which has a large degree of hairiness.
As is well known, spinning yarn has hairs at the surface of the yarn, and the aim of measuring thick irregularities and/or thin irregularities of the yarn is to investigate evenness or uniformity of the cross sectional area of the core part. If such irregularities exceed the permitted range then this will adversely affect the appearance of the cloth, and furthermore skin touch will be impaired and coloring irregularities may also result. Furthermore, if the yarn has significant thin irregularities then the tensile strength of the yarn will be reduced, and this will lead to yarn breakage during weaving. In this regard, since conventional electrical capacitance measuring devices and optoelectric measuring devices measure the whole of the yarn including the hairs, it is not possible to measure accurately thick irregularities and/or thin irregularities of the core part excluding the hairs.
On the other hand, defects in spinning yarn are not restricted to the abovementioned thick irregularities and/or thin irregularities, but also involve the state of hairs projecting from the surface of the yarn. Accordingly, if the hairs are unnecessarily plentiful or long then the warp and weft yarns will become entangled during weaving, reducing the ability to weave cloths. Further, the appearance of the woven cloth will not be good. In this regard, conventional electrical capacitance measuring devices and optoelectric measuring devices cannot detect such hair defects in independently.
On the contrary, bulky spun yarn which is soft to the touch must have sufficient hairs, and if there are too short or few hairs then this is a defect. However, with conventional electrical capacitance measuring devices and optoelectric measuring devices it is not possible to measure the state of the hairs independetly.
A device in which the optoelectrical measuring device has been improved is proposed in British Patent Application No. GB2064106A. According to this, a light source which emits scattered light onto the yarn, and a light receiving device which takes in the state of the exposure resulting from the yarn are provided, the construction is such that local lightness conditions are analyzed by means of a plurality of photosensors which are provided finely in the light receiving device, and it is explained that it is therefore possible to measure not only the core part of the yarn but also the hairy part.
However, according to the device of this British Patent Application it is necessary, in order to increase the measuring accuracy, to arrange a correspondingly large number of photosensors in matrix form, and therefore the cost is extremely high. Furthermore, since it detects the state of exposure of the yarn, stray light which is dispersed and reflected by the surface of the yarn is liable to have an effect, and there is therefore the problem that it is not possible to measure the state of the hairs accurately.